1 files changed, 112 insertions, 0 deletions
diff --git a/src/main/java/de/waldheinz/fs/AbstractFsObject.java b/src/main/java/de/waldheinz/fs/AbstractFsObject.java
new file mode 100644
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+++ b/src/main/java/de/waldheinz/fs/AbstractFsObject.java
@@ -0,0 +1,112 @@
+/*
+ * Copyright (C) 2003-2009 JNode.org
+ *               2009,2010 Matthias Treydte <mt@waldheinz.de>
+ *
+ * This library is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU Lesser General Public License as published
+ * by the Free Software Foundation; either version 2.1 of the License, or
+ * (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
+ * License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this library; If not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+ 
+package de.waldheinz.fs;
+
+/**
+ * A base class that helps to implement the {@code FsObject} interface.
+ *
+ * @author Ewout Prangsma &lt;epr at jnode.org&gt;
+ * @author Matthias Treydte &lt;waldheinz at gmail.com&gt;
+ * @since 0.6
+ */
+public class AbstractFsObject implements FsObject {
+
+    /**
+     * Holds the read-only state of this object.
+     */
+    private final boolean readOnly;
+    
+    /**
+     * Remembers if this object still valid.
+     */
+    private boolean valid;
+
+    /**
+     * Creates a new instance of {@code AbstractFsObject} which will be valid
+     * and have the specified read-only state.
+     *
+     * @param readOnly if the new object will be read-only
+     */
+    protected AbstractFsObject(boolean readOnly) {
+        this.valid = true;
+        this.readOnly = readOnly;
+    }
+    
+    /** 
+     * {@inheritDoc}
+     *
+     * @return {@inheritDoc}
+     * @see #checkValid()
+     * @see #invalidate() 
+     */
+    @Override
+    public final boolean isValid() {
+        return this.valid;
+    }
+
+    /**
+     * Marks this object as invalid.
+     * 
+     * @see #isValid()
+     * @see #checkValid()
+     */
+    protected final void invalidate() {
+        this.valid = false;
+    }
+
+    /**
+     * Convience method to check if this object is still valid and throw an
+     * {@code IllegalStateException} if it is not.
+     *
+     * @throws IllegalStateException if this object was invalidated
+     * @since 0.6
+     * @see #isValid()
+     * @see #invalidate() 
+     */
+    protected final void checkValid() throws IllegalStateException {
+        if (!isValid()) throw new IllegalStateException(
+                this + " is not valid");
+    }
+
+    /**
+     * Convience method to check if this object is writable. An object is
+     * writable if it is both, valid and not read-only. 
+     *
+     * @throws IllegalStateException if this object was invalidated
+     * @throws ReadOnlyException if this object was created with the read-only
+     *      flag set
+     * @since 0.6
+     */
+    protected final void checkWritable()
+            throws IllegalStateException, ReadOnlyException {
+        
+        checkValid();
+
+        if (isReadOnly()) {
+            throw new ReadOnlyException();
+        }
+    }
+    
+    @Override
+    public final boolean isReadOnly() {
+        return this.readOnly;
+    }
+    
+}